Charge Profile Analysis
Ion Exchange Chromatography for Peptide Charge Variants
Purpose
Charge profile analysis detects charge variants (deamidation, C-terminal truncation, succinimide formation) that may not be resolved by reversed-phase HPLC.
Method Comparison
| Method | Principle | Detects |
| CEX (Cation Exchange) | Positive charge binding | Deamidation, succinimide |
| AEX (Anion Exchange) | Negative charge binding | C-terminal variants |
| IEF (Isoelectric Focusing) | pI-based separation | Complex charge mixtures |
| icIEF (Imaged cIEF) | Real-time IEF | High-resolution charge profile |
CEX Method Parameters
| Parameter | Typical Value |
| Column | Wheat germ agglutinin (WGA) or sulfopropyl |
| Mobile Phase A | 20 mM MES, pH 5.5–6.5 |
| Mobile Phase B | A + 0.5 M NaCl |
| Gradient | 0–50% B in 30 min |
| Detection | UV 214, 280 nm |
| Flow rate | 0.5–1.0 mL/min |
| Column temp | 30 °C |
Charge Variants in Peptides
| Variant | Charge Change | CEX Retention | Cause |
| Deamidation (Asn→Asp) | −1 | Earlier | pH/temperature stress |
| Succinimide | −1 | Earlier | Asp/Gly sequences |
| C-terminal truncation | Varies | Varies | Process impurity |
| Oxidation | 0 (no change) | Slight | Met/Trp exposure |
| Aggregation | Varies | May not elute | Concentration |
🔗 Related: HPLC Analysis | Purity Analysis | Impurity Profiling